I always did like this "M-G pattern" lasgun design, it's nice to see it brought to life so well. One thing I wonder, though, is if there's really space on the top for the clip to be removed.
I'd always imagined the solar recharger to basically look like a meter square sheet of black mylar, or something, myself, that folded up into a little pack. Solar intensity in, say, North America is between 125 to 375 W/m². Therefore, you'd take around 3-10 seconds to get a minimum power shot let's say a Kilojoule (from Atomic Rocket [link] "Whether you use lasers or particle beams, you'll need a bit over a kilojoule of output energy to reliably incapacitate a human target. In the case of a laser weapon, that energy would be subdivided into ~1 joule pulses at ~5 microsecond intervals, to achieve penetration in the face of a laser's natural tendency to deposit energy at the target's surface.") but at least fourteen hours to fully charge a 19 megajoule power pack, which is one popular interpretation for '19 Megathule' in describing those clips. The other (which also has some supporting evidence) is that each trigger-pull shot on maximum power is 19 megajoules, in which case it would take a very long time indeed to fully charge a power pack with a solar kit, but then, this is perhaps appropriate, too. You could potentially get either energy requirement with the campfire method, though.
Of course, as they said way back in Rogue Trader, what technology there is in the forty first millennium, is by our standards, unbelievably advanced, and what looks advanced to us is so basic it's unworthy of mention. So you could potentially just set up a tiny device that gathers energy over a large area.
In any case, that nerdgasm over, I've got to say, this is a lovely piece, and my only suggestion is that you do a render of it fitted together.
to my knowledge, gw never actually made (and the black library never drew) what the solar attachment was supposed to look like so i had to take a blind guess at it. the technology we have these days is really inefficient and a lot of potential power is lost in reflections or absorption into the various layers that make up a solar cell, so im pretty certain it could be brought down to this size with higher grade materials and layered cells so more ultraviolet and infrared light could be harnessed within the same panel. if you imagine the kind of planet this would be used on, it would probably be a desert environment with a thinner atmosphere since i cant see it working at all in jungles or the heavily polluted urban settings. that said, its probably more likely that itd come as a cover for the backpack than an attachment like this, but that wouldnt fit on the shelf
in terms of how much power itd take to be effective, you also need to take into account the diameter of the beam. despite how bright lasguns tend to be, i think the dissipation over a material like plasteel (which endures well in hot and/or corrosive environments) would require the beam to be extremely narrow. a large number of tiny but deep punctures would still do some serious damage to your insides and could potentially require less power than a beefier beam overall, with a more powerful spike needed per shot to penetrate armour. in any case, youd probably use it in tandem with one or two of the external power packs so youd have a large reserve that builds up throughout the day whenever youre not busy being under attack.
i may well do a render of the whole thing set up together when i get around to it. at the moment all my time with 3d is going into trying to texture a realistic stormy sea, and ive been at that for months so dont hold your breath